A concept of a nuclear reactor buried below the lunar surface to make use of lunar soil as additional radiation shielding. The engines that convert heat energy to electricity are in the tower above the reactor, and radiators extend out from the tower to radiate into space any leftover heat energy. The power system would transmit 40 kilowatts of electric power, enough for about eight houses on Earth, to the lunar outpost.
Nuclear power could make a comeback beyond Earth if NASA goes forward with a proposed a fission reactor in its future moon base.
A fission-powered system could generate up to 40 kilowatts and give any lunar outpost enough power to supply eight houses on Earth. More importantly, astronauts will require a reliable and steady energy source on the moon and Mars.
"The problem with power on the moon is that, depending on where you're located, you may have 14 days of darkness," said Lee Mason, an engineer at NASA?s Glenn Research Center in Cleveland, Ohio, who heads the project. "We think nuclear offers some advantages there in terms of a continuous power source in sun or darkness."
Engineers envision a nuclear reactor buried under the surface of the moon so that lunar soil, known as regolith, can act as shielding against the reactor's radiation. Power converters would sit atop a tower jutting above the surface, changing the reactor's heat energy into electrical energy for astronauts to use.
The tower would also boast two 50-foot (15-meter) panels made of polymer composite material that could give off excess heat from the nuclear reactor.
Far-flung robotic missions, such as the Cassini orbiter currently orbiting Saturn, have relied on a different nuclear technology, Radioisotope Thermoelectric Generators (RTG), which draws on the energy from the natural decay of radioactive plutonium. Current RTGs produce roughly 100 watts of electricity, in comparison to tens of thousands of watts produced by nuclear fission reactors that split uranium atoms.
NASA previously launched just one nuclear reactor into space in 1965, but the experimental SNAP-10A reactor shut down after just 43 days of operation. Nuclear power made a brief reappearance in the Jupiter Icy Moons Orbiter (JIMO) proposal, but the mission was scrapped in 2005 due to budget constraints.
"JIMO was a little ahead of its time, a very ambitious program, and it didn't just quite fit in with the budget projections," Mason told SPACE.com.
Now the moon base proposal offers a new possibility, but Mason's NASA Glenn team must first decide which power converter engine to use for any nuclear reactor.
One design, a piston Stirling design from Sunpower Inc., of Athens, Ohio, uses two back-to-back piston engines that cancel out each other's mechanical vibration. The second design by Barber Nichols Inc. of Arvada, Colo., relies on a closed Brayton cycle engine that has a rotary system not unlike jet turbine engines. Both power converters can produce 12 kilowatts, or roughly 40 kilowatts in a pack of four.
NASA engineers hope to test the efficiency of power converters without the nuclear reactor in 2012 or 2013. A non-nuclear reactor simulator would provide the heat source for the tech demonstration on Earth, courtesy of NASA's Marshall Space Flight Center in Huntsville, Ala.
The space agency continues to ponder non-nuclear options such as solar power for a future lunar base. If NASA does use a nuclear reactor, it will resemble reactor technology that the U.S. Department of Energy (DOE) "has operated for many years," said John Warren, executive head of NASA's Space Power Systems Program in Washington, D.C.
Mason said that the project should finish on schedule if it continues receiving the $10 million funding shared between NASA and the DOE.
"We would like to design a system that can last eight years without any maintenance whatsoever," Mason said. "The technology is there to achieve that."
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